The present invention relates to a method of selectively reforming an inner part of an inorganic body by irradiation with a condensed pulsed laser beam and a new inorganic body produced thereby.
When an inorganic body containing rare earth or transition metal ion is subjected to oxidization-reduction or irradiated with an X-ray or ultraviolet beam, a valence of the rare earth or transition metal ion changes. For instance, J. Qiu et al. reported change of Eu2+ to Eu3+ by irradiating Eu2+-containing fluoride with an X-ray or ultraviolet beam, in Appl. Phys. Lett. 71 (1997) 759. W. A. Weyl reported change of Mn2+ to Mn3+ by irradiating Mn2+-containing oxide with an ultraviolet beam, in Coloured Glasses, Society of Glass Technology (1951).
In order to realize valence change of rare earth or transition metal ion at a specified part of an inorganic body, the inorganic body is covered with a shading mask having a predetermined pattern, and then selectively irradiated with an Xray or ultraviolet beam. The valence of the ion is partially changed at a part defined by the pattern of the shading mask.
Valence of rare earth or transition metal ion can be also changed by an oxidization-reduction method in a controlled atmosphere. In this case, valence change occurs over a whole of the inorganic body, but it is difficult to selectively change a part of the ion in the inorganic body. On the other hand, valence change of ion induced by irradiation with a X-ray or ultraviolet beam depends on a reaction in one photon process, so that an energy of the X-ray or ultraviolet beam is absorbed in a surface layer of the inorganic body. As a result, it is difficult to selectively change valence of the ion only at an inner part of the inorganic body.
Conventional methods have difficulty for selectively changing ion valence at a specified inner part of an inorganic body, as above-mentioned.
The present invention is accomplished to overcome such the problems as above-mentioned. The present invention aims at provision of a new inorganic body improved in functionality by selective valence change of rare earth or transition metal ion at its specified inner part. The selective valence change is realized by irradiating an inorganic body containing rare earth and/or transition metal ion with a condensed pulsed laser beam of wavelength different from absorption wavelength of the rare earth and/or transition metal ion.
According to the present invention, a pulsed laser beam of wavelength different from the absorption wavelength of rare earth and/or transition metal ion emitted to an inorganic body containing rare earth and/or transition metal ion in a manner such that a focal point of the pulsed laser beam is adjusted to an inner part of the inorganic body. Such condensing irradiation induces valence change of the rare earth and/or transition metal ion only at the focal point and its vicinity.
The inorganic body may be a glass or crystal containing one or more of oxides, halides and chalcogenides. Rare earth ion may be one or more of Ce, Nd, Pr, Sm, Eu, Tb, Dy, Tm and Tb ions. Transition metal ion may be one or more of Ti Mn, Cr, V, Fe, Cu, Mo and Ru ions.
When the focal point is relatively shifted with respect to the inorganic body, a domain with a predetermined pattern where the rare earth and/or transition metal ion changes its valence is formed at an inner part of the inorganic body. The pulsed laser beam is with pulse width under a picosecond.